The present invention relates generally to systems for cooling. More specifically, the present invention relates to a variable capacity vapor compression cooling system.
Cooling systems in the HVAC (heating, ventilation and air conditioning) industry are well known. By way of example, a schematic diagram of a typical cooling system is shown in FIG. 1 herein, labeled prior art. Referring to FIG. 1 herein, water enters an evaporator 12 through an input 14 where it is circulated through tubes within the evaporator and exits through an output 16. Liquid phase refrigerant enters evaporator 12 at an input 20 and evaporated refrigerant is delivered to a compressor 22 (e.g., a helical twin screw type compressor, which are well known in the art). Compressed vapor phase refrigerant is passed through an oil separator 24 for removing oil picked up in compressor 22. Thereafter the compressed vapor phase refrigerant is presented to a water cooled condenser 26 to condense the refrigerant to the liquid phase which is used for cooling, as is well known in the art. It will also be appreciated that air cooled condensers are well known and such could be used in place of the aforementioned water cooled condenser. Thereafter, liquid phase refrigerant is presented to an economizer 28 where vapor phase refrigerant (it is well known that a small portion of the refrigerant will be vapor, i.e., flash gas) is drawn off and delivered directly to the compressor. The liquid phase refrigerant is presented to input 20 of evaporator 12, thereby completing the cycle. When capacity of such a system is to be varied, it is common to unload the compressor using a slide valve control system, however, this is both inefficient and invariably, seriously complicates the overall design/cost of the compressor.